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    <div id="tip">今天的天气很好</div>
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        // console.log(a)

        // var a=1,b='1'
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        // console.log(a===b)

        // var sex='女',age=18,edu='本科'
        // var result=(sex=='男'||age==18&&edu=='本科')
        // console.log(result)

        // var a=1,b=2,c=3
        // var result=!(b>c)&&a<c||a>b
        // console.log(result)

        document.getElementById('tip').style.display='block'
        document.getElementById('tip').style.display='none'

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